Improving fruit set of ‘Kordia’ and ‘Regina’ sweet cherry with AVG  XII International Symposium on Plant Bioregulators in Fruit Production Orlando, Florida USA  28 July - 1 August 2013 Improving fruit set of ‘Kordia’ and ‘Regina’ sweet cherry with AVG Sally Bound1, Dugald Close1, Matthew Whiting2 1Perennial Horticulture Centre, Tasmanian Institute of Agriculture, University of Tasmania, Australia 2Washington State University, Prosser, USA This project has been funded by HAL using the cherry industry levy, voluntary contribution from the Washington Tree Fruit Research Commission and matched funds from the Australian Government

Australian Cherry Industry 2012/13 Total production = 15,500 t Exported = 3,256 t 59% (1,920 T) from Tasmania

Background Tasmania largest production state* 2,000 T in 2006/07 to 5,000 T (87% packout) in 2012/13 High quality reflected in price: Tas $13/kg vs other states $8/kg** Export to > 20 countries - freedom from fruit fly Vigorous rootstocks: Mazzard F12/1 and Colt Main varieties: Lapin, Simone, Sweetheart, Sylvia, Regina, Kordia, Sweet Georgia Regina and Kordia difficult to set fruit Industry grown from 2,000 T in 2006/07 to 5,000 T (=87% packout) in 2012/13 – largest production state* High quality reflected in price: Tas $13/kg vs other states $8/kg** Driven by export markets in Taiwan, Hong Kong (Chinese New Year) , Singapore, China, Malaysia (freedom from fruit fly) Kym Green Bush (KGB) training system of 10-15 uprights (better IRR as no trellis and easy to prune) on vigorous rootstocks, Colt and Mazzard F12/1 Main varieties: Lapin, Simone, Sweetheart, Sylvia, Regina, Kordia, Sweet Georgia Regina and Kordia difficult to set fruit under Tasmanian conditions Mainland growers have better success with dwarfing Gisela rootstocks, but access to these is limited in Tas * Fruit Growers Tasmania **Horticulture Australia Market Intelligence report

Objective to investigate the efficacy of Retain® (S)-trans-2-amino-4-[2-aminoethoxy]-3-butenoic acid hydrochloride (AVG) for improving fruit set on ‘Kordia’ & ‘Regina’

Methods – trial design Two trials: Kordia 2011/12 Regina 2012/13 Design: RCB with 5 replicates single tree plots Treatments: 3x2 factorial + untreated control 3 application times single application at 30% or 80% bloom, or double application at 30 & 80% bloom 2 rates 500 or 750 g Retain/ha (Kordia) 500 or 1,000 g Retain/ha (Regina)

Methods – treatment application Retain applied to whole trees by hydraulic hand lance 1 L spray per tree as a fine mist Retain application Kordia Regina 30% bloom 3 Oct 2011 6 Oct 2012 80% bloom 10 Oct 2011 11 Oct 2012 (Full bloom date) 11-12 Oct 2011 13 Oct 2012 organosilicone surfactant Maxx™ added to spray solution at label rate of 0.5 mL/L in ‘Kordia’ no surfactant used in the ‘Regina’ orchard

Methods – assessments two limbs per tree tagged & girthed flowers and fruit set counted on each tagged limb tagged limbs harvested individually fruit number & weight recorded % cracked fruit subsample of 25 fruit from each limb for quality analysis Assessments Kordia Regina (Full bloom date) 11-12 Oct 2011 13 Oct 2012 Bud/flower counts 11 Oct 2011 8 Oct 2012 Fruit set counts 18 Dec 2011 6 Nov 2012 Trial harvest 9 Jan 2012 14 Jan 2013 Flower counts Fruit set counts

Methods – quality assessments weight size (diameter and height) skin colour flesh firmness (BioWorks Firmtech & Guss FTA) skin puncture stem pull force total soluble solids pH titratable acidity

Results: Fruit set Kordia - 3 weeks before harvest Regina - 10 weeks before harvest No significant differences for - Retain rate, or - time of application (30% bloom, 80% bloom or 30 & 80% bloom

Results: Fruit set / spur Kordia Regina No significant differences for - Retain rate, or - time of application (30% bloom, 80% bloom or 30 & 80% bloom

Results: % cracked fruit Kordia Regina No treatment effect - minimal cracking in 2012/13 due to dry season 2011/12 was a very wet season and there were major problems with fruit cracking, but Retain treated trees showed significantly less cracked fruit than controls, reducing the incidence of rain-cracked fruit from 25% to 14% in the ‘Kordia’ orchard. The 2012/13 season when the Regina trial was conducted was a dry season and there was very little cracking. 44% reduction in cracking with Retain No significant differences for - Retain rate (500 or 750 g/ha), or - time of application (30% bloom, 80% bloom or 30 & 80% bloom)

Results: Fruit weight Kordia Regina No sig difference between Retain treated and control In the Regina trial Retain had no effect on fruit weight, but weight was lower in the Kordia fruit by 1.6 g Fruit weight lower in Retain treatments

Results: Fruit weight Kordia Regina In both cultivars the higher rate of Retain reduced fruit weight by approx 0.5 g Higher rate reduced fruit weight in both varieties

Results: Fruit weight Kordia Regina Double application reduced weight No difference with application time The double application of Retain reduced fruit weight by 0.8 g compared with the early application and 1.5 g compared with the 80% bloom application. Application time had no effect on Regina fruit weight. Double application reduced weight

Results: Fruit size Kordia Regina Kordia Control fruit were 1.3 mm larger in diameter than Retain treated But in Regina, Retain improved fruit size slightly (0.25 mm) Untreated Kordia fruit were approx 3.2 mm larger than Regina Conflicting results between 2 varieties

Results: Fruit size Kordia Regina Fruit diameter was reduced by the higher Retain rate in both varieties Higher rate reduced fruit size in both varieties

Results: Fruit size Kordia Regina The double application reduced fruit diameter by 0.7 mm cf 30% bloom application and 1.5 mm cf 80% bloom application in the Kordia But had no effect in Regina. The difference between the double application and 30% bloom was 0.4 mm Double application reduced size in Kordia but not Regina

Results: Fruit flesh firmness Kordia Regina Fruit flesh firmness results differed for the two varieties In Kordia, Retain treated fruit were firmer But softer in Regina Firmness of untreated was similar in both cultivars Conflicting results across 2 varieties

Results: Fruit flesh firmness Kordia Regina The higher Retain rate reduced firmness in both varieties Higher Retain rate reduced firmness in both varieties

Results: Fruit flesh firmness Kordia Regina Double application highest firmness in both varieties

Results: Fruit skin puncture Kordia Regina Retain application increased skin strength in Kordia but had no effect on Regina fruit Higher application rate reduced skin strength in Regina, but application rate was not significant in the Kordia Retain increased skin strength in Kordia but not in Regina Higher application rate reduced skin strength in Regina

Results: Stem pull force Kordia Kordia Stem pull force of Kordia fruit was lower in retain treated fruit cf the control fruit The double application also resulted in reduced stem pull force but Rate had no effect Similar trends were observed in the Regina but they were not significant No significant differences for - Retain rate (500 or 750 g/ha) Similar trends in Regina but not significant

Results: other quality parameters Retain had no effect on: - TSS - juice pH - titratable acidity - skin colour

Conclusions Positive effects were observed on fruit set - 57% fruit set increase in Kordia - 33% fruit set increase in Regina Reduction in fruit cracking Inconsistencies in fruit weight, diameter & firmness Reduction in stem retention No effect on other quality parameters Conclude that Retain is beneficial, but need to clarify effect on size and firmness Retain applications increased fruit set by 57% in ‘Kordia’ and 33% in ‘Regina’, compared to untreated control trees. We found no significant differences between the two application rates, nor was there any effect of application timing. In the ‘Kordia’ orchard we recorded a slight (4.4%) reduction in fruit diameter in the Retain-treated trees. The double application also reduced size by 3.7% compared with a single application (p<0.01). However fruit size was increased slightly (2%) by the lower, but not the higher, rate of Retain in the ‘Regina’ trial (p<0.001). Retain reduced the incidence of rain-cracked fruit from 25% to 14% in the ‘Kordia’ orchard. Fruit firmness in ‘Kordia’ was significantly higher in the Retain-treated fruit than the control fruit (7%), but stem retention force was reduced by 16%. This work has demonstrated that Retain may be useful for improving fruit set (yield) in sweet cherry cultivars that are chronically low-yielding. Further work is needed to substantiate these results in different production regions and clarify the effect of Retain on fruit firmness.

Thanks to…… Steve Paterson and Justin Direen for technical support Nic Hansen from Cherries Tasmania for use of trees Horticulture Australia and the Australian cherry industry for funds Valent BioSciences for provision of Retain